Exodus 12:12-13

For I will pass through the land of Egypt this night and will smite all the firstborn in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgment [proving their helplessness]. I am the Lord. The blood shall be for a token or sign to you upon [the doorposts of] the houses where you are, [that] when I see the blood, I will pass over you, and no plague shall be upon you to destroy you when I smite the land of Egypt. [I Cor. 5:7; Heb. 11:28.]